Piston actuated automatic drain filter

ABSTRACT

This invention relates to an air line filter of the type having a replaceable filter cartridge adapted to remove both entrained solids and fluids, the latter being dumped automatically by a piston-actuated drain valve each time the air flow shuts off. More specifically, the instant invention relates to an improved version of such filter in which one or more bypass passages break the seal between the valve element and its seat so that the Oring forming the seal is not drawn from its groove into a position where it will be damaged upon a downstream demand that returns the valve to closed position prematurely.

United States tent [1 1 Winter Feb. 26, 1974 PISTON ACTUATED AUTOMATICDRAIN FILTER Inventor: Jon E. Winter, Lakewood, Colo.

Primary Examiner-Tim R. Miles Assistant Examiner-William Cuchlinski, Jr.

Attorney, Agent, or FirmEdwards, Spangler, ['73] Assignee: WilkersonCorporation, Englewood, Wymore & Klaas Calif.

[22] Filed: June 21, 1971 [57] ABSTRACT 211 Appl' 155 111 This inventionrelates to an air line filter of the type having a replaceable filtercartridge adapted to remove both entrained solids and fluids, the latterbeing [52] US. Cl 55/218, 55/466, 137/204 dumped automatically by apistomactuated drain [Sl] Int. Cl B0143 33/38 valve each time the flowShuts ff More Specifi [58] new of Search 55/218 cally, the instantinvention relates to an improved ver- 55/466; 137/204 sion of suchfilter in which one or more bypass passages break the seal between thevalve element and its [56] References Cited seat so that the O-ringforming the seal is not drawn IT AT PATENTS from its groove into aposition where it will be dam- 2,6l9,l06 11/1952 Wilkerson 137/204 ag dupon a downstream demand that returns the 3,261,146 7/1966 Malec 55/218valve to closed position prematurely. 3,668,837 6/1972 Gross 55/218 X2,869,570 1/1959 Wilkerson 137/204 3 Clams, 5 Drawing FiguresPATENTEBmaze I974 INVENTOR JON E. WINTER 5 W wfo w TER For some time anair line filter has been successfully marketed in which the air flow isdirected through a replaceable tubular cartridge housed inside a hollowbody. As the entrained solids impinge against the cartridge wall, theydrop out as the result of a conventional screening action. The entrainedfluids, on the other hand, pass through the minute capillary passages ofthe filter element and, because of the resulting drop in pressure, dropout and are collected in a sump.

In the bottom of the bowl is a spool-type drain valve encircled by anO-ring that seals against the cylindrical wall of a tubular seat thathas a chamfered generally frustoconical entryway. Fluids collected inthe sump in the bottom of the bowl are discharged through the drainvalve. This drain valve reciprocates between its seated and unseatedpositions and actuation thereof is accomplished automatically by meansof a springbiased piston that drops down each time the air flow stops.As long as there is a downstream demand, the air pressure against theunderside of the piston is sufficient to overcome the spring bias andhold the drain valve closed.

Filters of this type that operate automatically on a demand basis, ofcourse, are subject to repeated actuations with the intervaltherebetween being relatively short. On occasion, it has been found thatthe O-ring becomes damaged to the extent that the seal provided therebyfails resulting in a leak. Apparently what actually takes place is thatas the spool moves down toward open position, instead of the seal beingbroken when the O-ring moves onto the chamfered entryway, it expands andmaintains brief sealed contact therewith. This occurs because theinterior bowl pressure is higher than atmospheric and a differentialpressure exists across the O-ring that acts outward radially maintainingthe seal even onto the upper part of the flared wall surface rather thanbreaking it as soon as the O-ring moves down off of the cylindricalsurface of the seat. So long as the drain valve spool continues to movedown toward open position, no problem arises because eventually theentryway will widen out to a degree where the O-ring can no longerremain in sealed contact therewith. If, on the other hand, a suddendownstream demand occurs which reverses the direction of the valveelement before it has opened for enough to break the annular seal, theO-ring will be trapped in this partially extended position where it issubjected to a shearing action as it moves back up across the annularcorner defined by the intersecting conical and cylindrical seatsurfaces.

It has now been found in accordance with the teaching of the instantinvention that this problem can be completely eliminated by the simple,but unobvious, expedient of providing the seat with one or more bypasspassages positioned and adapted to instantly drop the bowl pressure toatmospheric as soon as the valve element starts to open thus eliminatingthe differential pressure condition responsible for expansion of the O-ring into a position where it is subject to the shearing action of theseat corner.

Accordingly, it is the prime object of the present invention to providea novel and improved cartridge type air filter equipped with bypassmeans operative to equalize the air pressure inside and outsidethe bowlthe instant the valve element starts to open so that the O-ring sealwill not expand under the influence of a differential pressure impressedthereacross and move out of its groove into a position where it issubjected to a shearing action at the edge of the seat.

Another object is to provide the aforementioned improved version of thefilter without having to alter the basic structure thereof in any mannerother than to introduce one or more bypass grooves into the surface ofthe seat.

Further objects are to provide a filter of the type forming the subjectmatter hereof that is more reliable than its unimproved prior artcounterpart, one that is virtually leakproof except when dumping fluidas intended, and a unit of the class described that is virtuallymaintenance-free except for periodic replacement of the filtercartridge.

Other objects will be in part apparent and in part pointed outspecifically hereinafter in connection with the description of thedrawings that follows, and in which:

FIG. 1 is a diametrical section showing the improved cartridge-typefilter of the present invention in its entirety;

FIG. 2 is an enlarged fragmentary detail showing the drain valve spoolin diametrical section and in closed position;

FIG. 3 is a fragmentary detail much like FIG. 2 and to the same scalerevealing the drain valve in open position;

FIG. 4 is a bottom plan view of the drain valve seat showing the bypasspassages introduced into the frustoconical entryway thereto;

FIG. 5 is a still further enlarged fragmentary sectional detail showingthe O-ring encircling the drain valve spool in relation to thefrustoconical entryway to the seat and the groove in the latter thatconstitutes the bypass by means of which the positive bowl pressure isdumped the instant the O-ring reaches said entryway during its excursiontoward open position.

Referring next to the drawings for a detailed description of the presentinvention and, initially, to FIG. 1 for this purpose, reference numeral10 has been selected to designate the cartridge-type filter in itsentirety while numeral 12 refers to the body thereof and numeral 14 thebowl detachably connected to the latter. The body has an invertedgenerally cup-shaped configuration, its lower margin being bordered by aplanar surface 16 adapted to rest atop a flange l8 encircling the upperend of the bowl and form a fluid tight seal therewith. An integrallyformed annular skirt 20 extends down from the top 22 of the body spacedinwardly of the inside surface 24 of its outside wall 26 so as tocooperate therewith in defining an annular cavity 28. The inside surface30 of this skirt is cylindrical and forms a cylinder wall within whichpiston 32 reciprocates. An air intake passage 34 connects the exteriorof the body with annular cavity 28 through outside wall 26. Air outletpassage 36, on the other hand, connects the interior of the cylinderwith the exterior of the body across annular cavity 28 withoutcommunicating with the latter.

The interior of the bowl is shaped to define an upwardly facing annularledge 38 containing an O-ring groove 40 within which is seated an O-ring42. Resting atop this ledge in continuous annular sealed contact r withthe O-ring is a partition wall 44 having an integrally-formed tubularportion 46 that passes down and out through a central opening 48 in thebottom of the bowl where the externally-threaded neck 50 thereof issecured by a nut 52. Nut 52, upon being tightened on the threaded neck,abuts the bottom 54 of the bowl and, in turn, draws the partition walldown into sealed contact atop the O-ring. An external O-ring groove 56borders the tubular portion 46 above the neck and is provided with anO-ring that seals against the cylindrical wall surface bordering thebowl opening 48.

Bridging the gap between partition wall 44 and the lower margin of skirtis a tubular filter cartridge 58. An upstanding annular flange 60 on thetop of the partition wall cooperates with a similar flange 62 on thelower margin of the skirt to hold the cartridge centered therebetween.Air and entrained contaminants entering the air inlet must pass into theannular cavity 28 where the cartridge screens out the solid particles.The air along with the remaining entrained fluids pass through thecapillaries of the filter cartridge and are released into expansionchamber 64 at a lower pressure where the fluid contaminants drop out andare collected in the sump at the base thereof.

An upstanding tubular section 66 is formed integrally atop the partitionwall and provides a coaxial continuation of the lower tubular section46. This upper section has a vertical drain slot 68 therein whereby thefluids deposited in the bottom of the sump can drain on down into thelower section 46 where they either pass on out of the bowl past thechamfered entryway 70 to the cylindrical portion 72 of the spool valveseat 74 contained therein or, alternatively, are deposited in areservoir 76 located between the bottom of the bowl and the portion wall44. Shunting the fluids off into the reservoir is made possible by ports78 in the wall of the lower tubular section 46 and this occurs wheneverthe spool valve 80 is closed.

Piston 32 carries an annular O-ring groove 82 within which is mountedO-ring 84 which reciprocates therewith in fluid-tight sealed contactwith the cylinder wall 30. The piston is generally funnel-shapedalthough the neck 84 thereof has no opening therethrough in the mannerof most funnels. Instead, an internally flanged nut 86 screws onto thelower end thereof and is used to loosely fasten and suspend the spoolvalve therefrom. A coiled compression spring 88 resting atop supports 90inside the piston bowl 92 and abutting the underside of the top wall ofthe body normally biases the piston along with the spool valve attachedto the bottom thereof into open position. The piston has a bleed port 94in the wall thereof sized to pass enough air to prevent it from risingagainst the bias of spring 88 should a leak develop downstream.

During normal operation, the unit dumps moisture each time the air flowstops. Where no air flows, piston 32 is in the lower position thereofshown in FIG. 1 and the fluid in the reservoir 76 will drain from thebowl through ports 78 and lower tubular portion 46. When a downstreamdemand for air occurs, the air pressure above piston 32 drops to a levelwhere the pressure in chamber 64 exceeds the bias exerted by spring 88thereby pushing the piston up to a level where the air outlet passage 36is uncovered and air can flow to satisfy the demand. As this occurs, thespool valve 80 is raised by the piston into closed position against thecylindrical section 72 of the seat 74 thus closing off the reservoir 76.At the same time, however, the upper frustoconical section 96 of thespool valve 70 will leave the cylindrical section 72 of the seat andpass into the oversize interior 98 of the upper tubular section thusallowing fluid to pass under the influence of the positive pressure inchamber 64 through the drain slot 68 and down into the reservoir. Oncethe air flow. stops, the spring will return the piston and valve to itslower position as the pressure in chamber 68 bleeds off through port 94.

Now, the lower frustoconical section 100 of the spool valve is separatedfrom the enlarged cylindrical section 102 at the end thereof by anannular groove 104 containing an O-ring 106, all of which is revealedmost clearly in FIGS. 2, 3 and 5 to which reference will now be made.Looking particularly at FIGS. 3 and 5, it will be seen that as the spoolvalve raises up and moves into cylindrical seat section 72, the O-ring106 will first engage the chamfered entryway and be compressed into thebottom of its groove 104. It is then free to ride on up into thecylindrical section of the seat in continuous annular fluid-tight sealedcontact therewith as shown in FIG. 2.

The problem arises when the spool valve is moving toward open positionand the air pressure in annular cavity 108 between the upper and lowerspool sections 96 and exceeds the atmospheric side of the latter. Asthis condition occurs, the high pressure will enter O-ring groove 104from above and attempt to maintain the O-ring in sealed contact with theflared surface at the entryway to the seat by stretching and elongatingit. If, then, with O-ring 106 no longer bottomed in its groove 104, adownstream air demand causes the spool valve to change direction beforesuch seal has been broken, the O-ring will be caught and pinched betweenthe lower outside corner 110 of said groove and the corner 112 definedby the intersecting conical and cylindrical seat surfaces causing it tobe sheared or damaged. The eventual destruction of the O-ring to thepoint where it will no longer seal the spool-valve within its seat ismore or less inevitable.

With reference to all of the figures of the drawing, it can be seen thatthe above described shortcoming of the prior art drain valve can beeliminated by the simple, but unobvious, expedient of providing thechamfered entryway to the seat with one or more bypass grooves 114positioned and adapted to instantly equalize the air pressure above andbelow O-ring 106 just as it leaves the cylindrical section of the seatand before it has an opportunity to expand within its groove 104. In theparticular form illustrated, four such grooves 114 are used spacedequidistantly around the entryway. Note in FIG. 5, that just as theO-ring reaches corner 112 on its downward excursion, it will open thebypass passages 114 thereabove and equalize the pressure.

What is claimed is:

1. In an air line filter of the type having a body with an inlet and anoutlet connectable into an air line, a bowl detachably connected to thebody cooperating therewith to define a pressure chamber, said bowldefining a reservoir adapted to catch fluid contaminants and having adrain opening in the bottom thereof, an upstanding hollow cylindricaldrain tube with a chamfered entryway at its lower end mounted within thedrain opening, a valve member mounted within the drain tube forreciprocal movement between a closed position in the cylindrical portionthereof and an open position beyond its chamfered entryway, an O-ringseal encircling the valve element in fluid-tight sealed relation to thecylindrical portion of the drain tube, and a the passage forming meanscomprises at least one groove in the chamfered entryway communicatingthe interior of the cylindrical portion.

3. The improvement as set forth in claim 2 in which: the groove opensinto the cylindrical portion at a point spaced sufficiently far abovethe entryway to equalize the bowl pressure before the O-ring passes intothe chamfered portion.

1. In an air line filter of the type having a body with an inlet and anoutlet connectable into an air line, a bowl detachably connected to thebody cooperating therewith to define a pressure chamber, said bowldefining a reservoir adapted to catch fluid contaminants and having adrain opening in the bottom thereof, an upstanding hollow cylindricaldrain tube with a chamfered entryway at its lower end mounted within thedrain opening, a valve member mounted within the drain tube forreciprocal movement between a closed position in the cylindrical portionthereof and an open position beyond its chamfered entryway, an Oringseal encircling the valve element in fluid-tight sealed relation to thecylindrical portion of the drain tube, and a spring-biased piston-typevalve actuating means operatively connected to the valve member andmounted in the bowl for reciprocal movement in response to fluctuationsin pressure within the pressure chamber, the improvement whichcomprises: passage-forming means interconnecting the cylindrical andchamfered portions of one drain tube operative upon movement of theO-ring across the juncture therebetween to equalize the pressure insideand outside of the bowl.
 2. The improvement as set forth in claim 1 inwhich: the passage forming means comprises at least one groove in thechamfered entryway communicating the interior of the cylindricalportion.
 3. The improvement as set forth in claim 2 in which: the grooveopens into the cylindrical portion at a point spaced sufficiently farabove the entryway to equalize the bowl pressure before the O-ringpasses into the chamfered portion.